The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A vehicle includes a power plant, such as an internal combustion engine that drives a transmission and a driveline to propel the vehicle along a surface. More specifically, the power plant generates drive torque that is multiplied by a gear ratio through the transmission. The drive torque drives a differential that directs the drive torque to driven wheels, that provides a final gear reduction, and that transmits drive torque to the wheels while allowing them to rotate relative to one another (i.e., at different speeds).
Although the differential enables the driven wheels to rotate at different speeds, the differential can be damaged or scored with an excessive difference in wheel speed or ΔRPM across the differential. A ΔRPM across the differential can occur when the driven wheels are on surfaces having different frictional coefficients. For example, if one wheel is on a low frictional surface (e.g., ice) and the other is on a higher frictional surface (e.g., dry pavement), the wheel on the lower frictional surface can rotate at a higher speed than that on the higher frictional surface.
If the differential is damaged as a result of experiencing an excessive ΔRPM for an extended period, the differential must be replaced. In some instances (e.g., front wheel drive vehicles), the differential is integrated into the transmission. As a result, the cost to replace the differential is compounded by the additional work required to access the differential within the transmission.
Accordingly, vehicles implement a differential score protection (DSP) control to prevent damage to the differential. Traditional DSP control regulates engine torque output when wheel slip occurs. More specifically, the traditional DSP control decreases engine torque to reduce engine output power, allowing the wheels to grip their respective surfaces and to resolve the wheel slip condition.
The amount of engine torque reduction is calibrated based on various ΔRPM values. This calibration, however, is time and cost intensive. More specifically, a calibration engineer must develop the calibrations to resolve the wheel slip condition, while providing sufficient drivability or feel for the vehicle operator. For example, the vehicle operator should not perceive excessive power sags or surges while the DSP control is active. Also, when the DSP control goes inactive, a calibration is provided to ramp the engine torque out of the DSP mode.
The DSP control is executed by a control module, which can be supplied by multiple manufacturers for a single vehicle platform. As a result, the calibration process is compounded because the calibration parameters developed for a particular vehicle must be translated for the various control module types. For example, if the calibration parameters require an engine torque decrease of X Nm for a ΔRPM of Y, the control modules interpret the X Nm value differently and therefore must be correspondingly calibrated to provide the proper engine torque reduction response based on the particular control module that is used.